AE memory and multiprocessing prefs

Hi all.
Just wondering what my optimal setting are for AE cs4 and me. I have a 2x2.8 Ghz Quad-Core Intel Xeon with 8GB ram. In my preferences whats my optimal settings, I tend to see errors or freezes if i adjust them. Especially when i attempt to render frames simultaneously. I tend to do rather large projects with lots of motion blurs and other render heavy settings. Also i am using a ATI Radeon HD 2600, if i upgrade will it boost performance and if so any recommendations that wont break the bank?
Thx in advance
john

8 GB of RAM is probably not enough to feed all 8 cores of your computer, so you should either use "CPUs to leave for other applications" to restrict the number of processes AE runs, or disable multiprocessing entirely.

Here are some tips for performance I posted recently:

There isn't a simple formula for determining what will get you the best performance, because your computer isn't the only factor; your footage, your effects, and your workflow all impact performance.

As general guidelines for AE performance, I always recommend a system configuration that includes:

A 64-bit edition of your operating system

Multiple cores or processors

Between 2-4 GB of RAM per processor core

A fast RAID or 3 separate hard drives (one for the OS and apps, one for source footage, and one for renders)

The most current release of AE (the 9.0.2 update fixes quite a few quirks for AE CS4)

I also recommend adjusting your workflow to accommodate AE's strengths and weaknesses:
Transcoding any interframe-compressed media like MP4 to an intraframe codec before importing
Turning off OpenGL for previews and rendering
Using proxies or pre-renders where appropriate
Use a region of interest where appropriate
Using Shift-RAM preview with lower quality settings than RAM preview for quick takes on your work

Finally, I'd refer to you a couple important links. Todd Kopriva (AE's documentation lead) has written two important blog posts on performance: